Bugs, found by valgrind

sql/item_cmpfunc.cc

@@ -6278,8 +6278,8 @@ longlong Item_equal::val_int()
   while ((item= it++))
   {
     Field *field= it.get_curr_field();
-    /* Skip fields of non-const tables. They haven't been read yet */
-    if (field->table->const_table)
+    /* Skip fields of tables that has not been read yet */
+    if (!field->table->status || (field->table->status & STATUS_NULL_ROW))
     {
       if (eval_item->cmp(item) || (null_value= item->null_value))
         return 0;

sql/sql_select.cc

@@ -24183,6 +24183,8 @@ int JOIN::save_explain_data_intern(Explain_query *output, bool need_tmp_table,
 
     explain->select_id= join->select_lex->select_number;
     explain->select_type= join->select_lex->type;
+    explain->using_temporary= need_tmp;
+    explain->using_filesort=  need_order;
     /* Setting explain->message means that all other members are invalid */
     explain->message= message;